The present invention relates to a control apparatus for controlling a drive of a motor. More specifically, the present invention relates to a control apparatus for controlling a position of a motor using a position detector.
FIG. 9 is a block diagram showing a conventional door drive controller using a linear motor. The conventional door drive controller includes a door 1; a linear motor 2 having a movable part for driving the door 1; a position detector 3 for detecting a position of the movable part of the linear motor 2; a link 4 for linking the door 1 and the movable part of the linear motor 2; a lock 5 as locking means for mechanically locking the link 4 when the door is closed; and a motor drive controller 6 for driving the linear motor 2 based on a reference position data.
The motor drive controller 6 includes a reference current calculator 7 for calculating a reference current value based on a deviation between a reference position and a detected position detected by the position detector 3, and an electric power converter 8 for supplying a current corresponding to the reference current value calculated by the reference current calculator 7.
When the door 1 is opened and closed, first, the position detector 3 detects a position of the movable part of the linear motor 2 linked to the door 1 via the link 4. The reference current calculator 7 in the motor drive controller 6 calculates a reference current value supplied to the linear motor 2 based on the reference position and the detected position detected by the position detector 3. Then, the electric power converter 8 supplies an electrical current to the linear motor 2 according to the reference current value from the reference current calculator 7. When the door 1 is closed, the lock 5 mechanically locks the link 4 to keep the door 1 closed in a state that the current to the linear motor 2 is stopped. When the link 4 is locked mechanically, the movable part of the linear motor 2 connected to the link 4 is also locked.
When the position detector 3 is failed and outputs no position data, it is possible to determine that the position detector 3 is failed. However, when an incorrect position different from an actual position is outputted, it is not possible to detect the failure of the position detector 3. Further, if a position of the link 4 is shifted from that of the lock 5 due to aging, it is also not possible to detect the shift. Therefore, the actual position is not clearly detected, and it is difficult to correctly lock the link 4 to the lock 5, thereby making the door drive system imperfect and lowering the system reliability.
Further, in the case that the lock 5 does not mechanically lock the link, in order to keep the door 1 closed, it is necessary to continuously supply a current to the linear motor 2. As a result, it is necessary to increase the current capacity of the linear motor 2 and electric power converter 8, thereby increasing a manufacturing cost and a size of the door drive controller.
In view of the problems described above, an object of the invention is to improve the reliability of the door drive controller without increasing the current capacity of the electric power converter.
Further objects and advantages of the invention will be apparent from the following description of the invention.